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car is 91 318i
ive been searching and searchin and reading and so on, i will explain my problem and also sum of the things i have done

when the car is cold and i start it up the idle surges as normal and then when it goes to drop down to the usual 750rpm or so it seems like it just wants to die, so i give it sum gas and just hold the rev above 1500 for about 30 seconds or so, then slowly release, then it idles steady at 750. as the car idles after about 30 seconds i get check engine light (idle still smooth). give a shot of gas and check engine light goes away!

i noticed that the intake boot has all kinds of cracks in it, so i replaced it with a brand new one, seemed to help a bit
put in a new air filter also

now as i have searched could this be from either my AFM or ICV? would cleaning them clear this up? im kinda stumped

btw its not always at cold startup, it happended to me after i was driving on the highway for 2 hours and as i exited n came to a stop it happend again. car runs smooth when driving its just when its time to idle its a little iffy. n e help is greatly appreciated!

Well to simplify things, there are only a handful of things that control how the car runs. There's the air flow meter (AFM), the idle control valve (ICV), the oxygen sensor, the coolant temperature sensor (CTS), and vacuum. A vacuum leak can cause a car to idle poorly, but if it was a vacuum leak the car would idle poorly all the time. The CTS can be tested, the bentley service manual will tell you how to do that. You can try unplugging your oxygen sensor and see if it affects how the car runs (the car will run in an open loop mode off of a default engine map). If you know anyone else with an E30 you can try swapping AFMs and see if that makes a difference.

Another thing to check is the plugs, wires, cap and rotor. If they are old and tired they can start getting dicey.

If it was only a small vacuum leak the car wpuld only idle poorly when cold. As the engine warms up the expansion could all but close the vacuum leak. have you done a stomp test to see what code its giving you? The ecu will hd any thrown codes until you clear it.

I cleaned out my ICV with brake cleaner. The thing was all dirty and filled with dirt. Cleaned it out and now instead of a rough idle at all time, the car sits and purrrs a little bit better. I suggest you clean it out with brake cleaner and throw it back on. You'll see on the boot that it has a plug that connests to it and also feeds into 2 lines. Take it off and look at it, I bet it's filled with lots of dirt.

Another thing might be your AFM. Changing it over and seeing if that's the problem would be awesome. I know with the M30 AFM that was put on my car, I had to adjust the the spring inside. The car would die at normal operating temp. After I fixed the spring and let more air into the system, the car runs.

ok first thing on sunday im going to take out my ICV and clean it, clean my AFM, after all cleaned up n dry i will start my car and hope for the best, monday i will be going to my machanic up the street so he can tell me what code it is throwing when in idle, i will update on sunday to let u guys know what my finidngs are so far! thanx for all the help the E30 community has a wealth full of knowledge!

ok so i did the "stomp test" and the code is "1222" Lambda Control #1, now im gonna start by cleaning my AFM, check my plugs and wires (replace if needed), gas tank is full already, and see if this helps, will report back as soon as i am done! thanx Bullet Ride for that info!!

ok so i did the "stomp test" and the code is "1222" Lambda Control #1, now im gonna start by cleaning my AFM, check my plugs and wires (replace if needed), gas tank is full already, and see if this helps, will report back as soon as i am done! thanx Bullet Ride for that info!!

that code comes up with the computer is trying to sort out the air fuel mix. lambda control 2 is when you need to replace the o2 sensor. I had that happen on my 325is when it would sit and idle for a while during cold weather. revved the car and light went out.

ok so i check spark plugs, they seem fine, checked the wires, one of them that goes into the cap looks like sumthing broke/rotted so i cleared it out put it back in, going to replace it hopfully monday. took off the AFM and cleaned it with carb cleaner (wasnt that dirty), start the car, car was a little warm so it didnt want to die, idle seemed pretty rock solid. gonna start it later in the evening to see if it does it again. didnt get to the ICV cuz i have no idea where it is lol, and ive searched n searched. HOWEVER when the car is idling i still get the check engine. did stomp test again and still getting "1222" now im starting to think its the o2 sensor, as people have mentioned when the car idles, light comes on, when they rev, light goes away. thats the problem i am having now, so far.

does any one have or can explain where and how to test to see if my o2 sensor is bad? car is going in for safety this week so if it needs replacing i can bring it to my machanic for him to replace or even do it myself if its not to hard to get to.

O2 sensor isn't really a big deal. Mine is shot to hell but w/e. Your ICV is connected to your boot. You'll see the 2 vacuum lines that run into your brake booster, so that leaves you with another 2 lines that run to the ICV on the front of the boot (beside the AFM). It should have a plug that is connected to it. Unplug it and clean it out. Mine had black dirt inside it. After a good wash the idle seems a lot better.

does any one have or can explain where and how to test to see if my o2 sensor is bad? car is going in for safety this week so if it needs replacing i can bring it to my machanic for him to replace or even do it myself if its not to hard to get to.

O2 sensor is easy to replace, all you need is a 22mm wrench (I think) and I find it easiest to get at it from the bottom side of the car. If you need to replace it, make sure you spray a good helping of PB Blaster on it a few hours ahead of time.

ok thank u HavocSteve i will be looking for the ICV on monday to celan it. and thanx Bullet Ride this will also be tested on monday. will report back with my readings, hopfully i can solve this problem by 2morrow.

also one thing i want to add, when i had my car idleing 2day i was walking around the car, and noticed when i was near the exhaust, it smelled a little rich, so now im almost leaning towards o2 sensor. n e one can correct me if im wrong. also maybe FPR?